The present invention relates to the holding and culturing of crustaceans and more particularly to an apparatus and method for raising lobsters from the post larval stage to animals of marketable weight. The present apparatus and method may also be used for the storage and maintenance of naturally harvested lobsters prior to distribution and marketing.
The American lobster, Homarus americanus, is the victim of intense fishing pressure. Natural stocks are being exploited to maximum sustainable yield. During recent years, Canadian annual landings have ranged from 18-23 thousand tonnes and appear to have stabilized at that level.
The American lobster is recognized internationally as a connoisseur's delight. The market potential for this animal, especially as a live commodity, could far exceed the supply. There are presently several problems in the live lobster trade which are jeopardizing the live market, namely; inflated retail prices due to high risk of loss of the live lobsters, quality reduction with prolonged storage and intermittent supply. These factors have resulted in increased sales volumes for frozen whole lobsters because of reduced risk of loss, maintained quality with storage, and a supply that can be extended far beyond the fishing season.
The preferred commodity for the consumer is still the freshly cooked lobster. But in order to revitalize its proper market place, the problems of high risk, quality reduction and intermittent supply must be solved.
The live lobster industry uses communal holding tanks, floating cars and crates, and communal tidal pounds to store lobsters from time of landing to shipping. Approximately the percent of lobsters intended for live trade are lost to injury, disease cannibalism and poor water quality. Injuries encourage the spread of the disease Gaffkemia which is fatal to lobsters but has no effect on humans. Lobsters which become infected with this bacterium become lethargic and fall prey to more vigorous lobsters. During the "feast", millions of virulent bacteria are released, resulting in the infection of surrounding lobsters with skin lesions which act as "portals of entry" for the bacteria. The introduction of one Gaffkemic lobster into a pound of communally held lobsters can result in an epidemic and massive loss. When a shipment of lobsters is purchased from a pound, the present system gives no guarantee as to the incidence of disease. Incidence of disease can be determined by random blood sampling of the stock and determining whether or not Gaffkemia-causing bacteria are present in the samples, but this procedure is expensive and time consuming and has not been adopted by the industry. The inconsistency of the health status of pounded lobsters has persuaded many retailers to purchase the frozen commodity.
Potential spread of disease in communal pounding escalates with increased period of holding. Experienced pound operators turn over stock as quickly as the market dictates or as soon as mortalities start mounting. The high risk associated with holding over extended periods in an attempt to cash in on higher post season prices discourages this practice.
Extended holding results in reduced meat content. The rate of body metabolism of communally stored lobsters is excessive. Feeding of lobsters to deter cannibalism and shrinkage is only partially effective as a lobster's favourite diet, when available, is its own species.
Extended periods of communal holding can result in a high incidence of Gaffkemia, reduced meat content, mutilations and reduced physical appearance and a generally weakened condition making shipping and post shipping storage a volatile situation.
Each year more than $10 million worth of market lobsters are lost during holding due to disease, cannibalism and stress caused mortalities. These losses demonstrate gross inadequacies in the traditional holding facilities.
As mentioned above, the traditional facilities employed for lobster holding include tidal pounds, floating cars and crates, and land based communal holding tanks. These facilities are plagued with significant lobster mortalities due to disease (in particular, Gaffkemia), cannibalism, and stresses caused by overcrowding, physical injuries and fluctuations in water quality. The physical appearance of lobsters that do survive to be sold on the live lobster market is often poor due to claw, leg and antennae losses. Crowded lobsters mutilate one another. These injuries result in many lobsters being rejected by markets which demand "high product quality" and pay premium prices.
Communal holding systems have proven to be breeding grounds for Gaffkemia. This is due to the way in which Gaffkemia can be transmitted from lobster to lobster and the physiological effects on infected lobsters. In order for a lobster to become infected with Gaffkemia, the causative bacterium, Aerococcus viridans var. homari must enter through a lesion in the integument of the lobster. In communal holding, physical interactions of lobsters cause numerous lesions through limb losses and simple punctures in the integument. If bacteria are present in the water, they can enter a lesion before the natural clotting mechanism of the lobster seals the wound. Once the bacteria have entered, the lobster will die in a matter of days or weeks, depending on the water temperature. Once established in the lobster, the bacteria are responsible for a massive reduction in the blood's clotting ability, disfunction of the hepatopancreas, and reduction in the oxygen binding capacity of the hemocyanin. Infected lobsters become more lethargic with worsening infection. In communal holding, stronger lobsters will mutilate the lethargic ones. When an infected lobster is injured, its blood readily drains from its body. Literally millions of virulent bacteria are released into the surrounding water. As the surrounding lobsters fight to "feast" they in turn become wounded and consequently infected. Very few bacteria are required to trigger an epidemic of Gaffkemia in a communal holding operation.
When lobsters are kept physically isolated in individual holding compartments, where physical contact can be eliminated, the incidence of injury and possibility of infection is dramatically reduced. Even in a Gaffkemia infected water system, lobsters will not become infected unless physical injury occurs.
The need for a commercially viable, high density holding system is therefore obvious and immediate.
In the past, there have been numerous patents issued for systems and procedures for rearing of crustaceans in tanks, cages, or baskets. Most of these systems have completely ignored the biological requirements of the lobster and none have been proven commercially successful to this date.